Currently, there is interest in equipping passenger vehicles with passive seat belt systems having an upper torso restraint belt, more commonly known as a shoulder harness, that automatically extends itself across the upper torso of a front seat occupant upon the closing of the vehicle door adjacent to the seating position. In one known system, one end of the belt is anchored to an upper portion of the door frame, and the other end of the belt is anchored to a spring-loaded reel of a retractor mechanism mounted on the inboard side of the seating position. The retractor mechanism in this system permits the belt to protract from the retractor mechanism upon the opening of the door, and to retract upon the closing of the door.
The retractor mechanism preferably is of the vehicle sensitive inertia type. In this type of retractor mechanism, an inertia sensor comprising a pendulum device is engageable with a reel locking bar to drive the latter into reel latching engagement upon rapid acceleration or deceleration of the vehicle, as might occur during an accident, to prevent loss of the seat occupant restraint function of the shoulder harness.
One disadvantage of having the retractor mechanism on the inboard side of the seating position is that the mechanism excessively protrudes into the passenger compartment space. A second disadvantage, as discussed in U.S. Pat. No. 4,040,645 issued Aug. 9, 1977 to W. M. Giffen for a "Seat Belt Apparatus," is that the webbing of the shoulder harness is frictionally dragged across the seat occupant's clothing as the door is opened and closed. The alternative is to reverse the belt anchorage points by mounting the retractor mechanism within available space between the inner and outer door panels to receive the outer end of the torso belt and by connecting the inner end of the belt to an anchor device at the inboard side of the seating position. It has been found, however, that the rapid swinging movement of the door, as it is swung from or to a closed position, causes the inertia sensor to lock the reel. Without the necessary full protraction of the belt the door would not open and the seat occupant, undesirably, would be restrained against egress from the vehicle. Limitations on the retraction of the belt during closing movement of the door could result in a tangled or jammed belt, or an improper fit of the belt about the seat occupant's torso.
U.S. Pat. No. 3,866,944 issued Feb. 18, 1975 to K. Takahashi for a "Locking Device for Seat Belt for Vehicles," and the aforementioned U.S. Pat. No. 4,040,645, both recognize the desirability of relating the operation of the seat belt retractor mechanism to closure and opening of the vehicle door. The '944 patent discloses a number of ways of accomplishing the desired result, some of which are relatively complex mechanical linkage systems and others of which combine both electrical and mechanical operations for selectively controlling the unlocking of the retractor. The '645 patent discloses a much simpler system that uses a pendulum device operable in a conventional manner for moving a locking bar into ratchet plate engagement to lock a retractor reel against permitting belt protraction. A lever system responsive to the position of the vehicle door operates to block movement of the locking bar by the pendulum device when the vehicle door is open. The disadvantage of a lever system is that it is not fail safe and may jam in a manner to render the pendulum device inoperative to cause movement of the locking bar into ratchet plate engagement when needed.
The present invention embodies a simple mechanism to accomplish the desired function with greater assurance that the mechanism will be operative.